Will running Blender on RAM Drives increase Blender's "Speed"?
Reserving memory for a file system was a good idea 20 years ago. 

Modern operating systems use all the available memory that is left by the running processes for caching. 

When you start a program the first time it takes longer than subsequent starts because the files and used libraries are still available in RAM. This is the best way because if a process requires more memory cache areas can be evicted. A RAM-disc whereas would  statically allocate the memory which might be needed by another process and couldn't be temporarily released.

tl;dr

No, It would harm the overall performance of your system.